Reshape the IPY dcdamp filter of Xarm suspensions

[YoshinoriFujii]

Background

• In the performance test for seicSC, it was found that IP-T and L motion coupling to Xarm cavity signal looked dominant.
• I was also found that the ITMX and ETMX-IPY loop was different each other, and one of them did not feedback a force which was proportional to the velocity.

Todo

• shape the filters so that:

  • [ ] implement same shape filter to increase the CMMR.
  • [ ] the feedback signal is proportional to velocity

• [ ] Check the stability

• [ ] compare the spectra w/ implemented one vs. w/ newly implemented one.

[YoshinoriFujii]

Log on 2019.9.28

Modification plan

[YoshinoriFujii]

work log on 2019.9.29

After implementation

• The loop stability looked okay, in the time scale of a few hours.

• spectra comparison

  • w/o controls vs. w/ previous controls:

  • w/ previous controls vs. w/new controls:

[YoshinoriFujii]

During this measurement, an earthquake was happened. since comparing the spectra became difficult, I started to check the actuator coupling of IP stage.